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Toshiba 48L3451DB dead 17IPS20 Rev6 psu

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    #41
    Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

    here you go!
    Attached Files
    Last edited by notallbad; 07-02-2020, 06:51 PM.

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      #42
      Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

      Correct, no J19 jumper. red circle.

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        #43
        Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

        Although the component values do not match the schematic the layout looks identical.
        Budm was quite correct that the power supply should power up when disconnected from the main board i.e the 24V and 12V should be available at the connector without the need to provide any other signal. Just like Budm I cannot see how the supplies come up when pins 1& 2 are lifted.
        I have run a simulation of the circuit and the opto led definately needs to be switched on for Vcc to become available.

        With the power supply still disconnected from the main board and the opto in place what VCC_Main, +12VCC and VCC do you have. Pin1 of U201 looks like it's not quite soldered back in place.
        Attached Files
        Last edited by dick_barton; 07-03-2020, 04:51 AM.
        Willing to help but I'm no expert.

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          #44
          Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

          Opto soldered back in.
          Psu disconnected.

          VCC_Main at R246 - around 9v goes up to about 16v and drops
          +12VCC at R270/1 - goes up to about 12v but drops
          VCC at D200 - around 9v, goes up and down to about 12-14v
          Last edited by notallbad; 07-03-2020, 06:14 AM.

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            #45
            Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

            Those voltages seem to be reasonable but should not be bouncing. What DC voltage do you have between the two legs of C105? the large 450V capacitor.
            Willing to help but I'm no expert.

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              #46
              Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

              C105 sits around 336v, jumps to 400v then straight back down to 336v again.

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                #47
                Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                OK, so the PFC circuit appears to be switching on and off and would explain why the other supplies are not stable.
                Willing to help but I'm no expert.

                Comment


                  #48
                  Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                  U101 I believe is the PFC controller and requires a minimum of 11V to start it off and will stop if the voltage falls below 8.5V

                  You say VCC which I see also supplies U101, has 9 -12 - 16V and dropping so should be more than enough to start it off so why is the voltage dropping.

                  Can you check the components around that IC especially C127
                  Willing to help but I'm no expert.

                  Comment


                    #49
                    Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                    Can't really find anything wrong. nothing obvious at the moment.

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                      #50
                      Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                      Originally posted by notallbad View Post
                      Can't really find anything wrong. nothing obvious at the moment.
                      Are you able to swap the IC out?
                      Willing to help but I'm no expert.

                      Comment


                        #51
                        Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                        will look on spare boards I have otherwise, no.

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                          #52
                          Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                          have found U101 FAN7529 on an 17PW07-2 board.
                          Last edited by notallbad; 07-03-2020, 10:43 AM.

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                            #53
                            Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                            Swapped it over and got a steady 24v on CN4.
                            Plugged the psu back up into the tv and voltages back to fluctuating, even with the board isolated from main and backlights.

                            Not getting 400v across C105 either just sits at 340v.

                            Could it just be unlucky this one has gone faulty (it is a used part) or what could be 'blowing' them?
                            Last edited by notallbad; 07-03-2020, 11:54 AM.

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                              #54
                              Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                              Just ordered some up so at least I'll have a few spare in case the next one blows.

                              Comment


                                #55
                                Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                                With the mainboard disconnected from the power supply do you now have 390ish volts across C105 and the 12V & 24V supply. If the answer is yes then you may well have a mainboard problem supplying ST_BY voltage to the power supply.
                                Last edited by dick_barton; 07-03-2020, 03:22 PM.
                                Willing to help but I'm no expert.

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                                  #56
                                  Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                                  No, think the Fan7529 must have 'blown'.

                                  After plugging into mainboard I don't get 400v just sits at 336v, 12v and 24v fluctuating again, and this is whether its plugged into the main or not.

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                                    #57
                                    Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                                    But did the PSU look as though it was working when you changed the IC. You say you had a steady 24v after you replaced the chip.
                                    Willing to help but I'm no expert.

                                    Comment


                                      #58
                                      Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                                      Yh. I measured a steady 12v and 24v on CN4 then decided to plug it all up. Still.no sign of life then measured volts again to find the fluctuating 12 and 24v.

                                      Disconnected the main to find voltages still fluctuating and no 400v on c105 whereas before it was at least ramping up to 400v then dropping back to 336v.
                                      Last edited by notallbad; 07-03-2020, 03:50 PM.

                                      Comment


                                        #59
                                        Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                                        I think I'll replace the ic again and double check ALL voltages are steady and present then report back before connecting to the main.

                                        I have 8 ic's on there way so will have a few spare to play with.
                                        Last edited by notallbad; 07-03-2020, 03:51 PM.

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                                          #60
                                          Re: Toshiba 48L3451DB dead 17IPS20 Rev6 psu

                                          Replaced the Fan7529 ic but still just getting the 5v, 12v and 24v ramping up then dropping out.
                                          Reading across the main cap C110 just sits at 335/6v.

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